crozier



filed'gg ly 117 195 2 M. A. CROZIER 2,783,756

COMBINED FLUE AND CHECK DRAFT DAMPER UNIT 2 Shets-Sheet 1 a 56 I i 2.

1* INVENTOR. Mama .4. C/POZ/E/P A TTOF/VEY March 5, 1957 M. A. CROZIIER 2,783,756

I 1 COMBINED FLUE AND CHECK DRAFT DAMPER UNIT Filed Jfily'l'Y, 1952 2 Sheets-Sheet 2 IN VEN TOR. MIC/{4ft .4. CPOZ/fl? CHIMNEY 510E 6 FuAw/l CE SIDE United Patent I 2,783,756 COMBINED FLUE AND CHECK DRAFT DAMPER UNIT Michael A. 'Crozier, Mount Vernon, N. Y., assiguor to National Fuel'cons ervation Co., Inc, White Plains,

ift, a corporation of New York ,Application July 17, 1952, Serial No. 299,346

18 Claims. (Cl. 126-292) i invention relates to a control apparatus forimproving the thermal functioning of a furnace or boiler proving the transfer of the 'heat energy of the fuel tothe boiler or furnace medium, to make more effective the heat transfer areas or surfaces of the boiler or furnace, and to lessen heat losses to the chimney or stack, all while maintaining proper draft and even though .the

furnace installation meets with various factors 'of'vari ability. Another object is to provide a deviceorap paratus of the just-mentioned character which will be self-adjustable to variations or changes in the pressure of the gases of combustion and constructed and operat-' ing so as to require no manual setting or adjustment once it is initially set to function in a given installation.

Another object is to provide a compact unit form of device or apparatus of the above-mentioned character that is of simple, rugged, and durable construction, that can be inexpensively fabricated and assembled, and in which such movable parts as are exposed to the flue gases are movably mounted in a manner to resist such corrosive action of the flue gases as might detrimentally affect long-lasting ease and freedom of movability and gas-pressure responsiveness.

Another object is to provide a simple and compact unit-type of device or apparatus, of the above-mentioned kind, that can be easily and inexpensively installed, particularly in existing installations of boiler or furnace and chimney. Another object is to provide a device of the above-mentioned kind that can be speedily installed and in foolproof manner. Another object is to provide a device of the above character that can be readily assocoated with the flue or smoke" pipe that leads from the boiler or furnace to the chimney and, moreover, that is so constructed as to achieve such assembly to the flue and to achieve its intended functioning regardless of any angularity that the axis of the flue might have to the horizontal plane.

Another object is to provide a simple, dependable and foolproof mounting assembly of a device of the abovementioned character with its mounting or support, such as a flue pipe. More particularly, it is an object of this invention to facilitate the installation of the device or apparatus on or in a flue pipe, to avoid damaging mutilation of the flue pipe where the device is assembled to an existing installation, and to achieve assembly of the device and the flue pipe in a manner that dependably prevents misalinement or other inadvertent derangement as would cause binding or other interference of the flue pipe or parts thereof with moving or movable parts. of the device itself. Another object is to provide a device or apparatus of the above-mentioned kind with alining or securing means adapted automatically to coact with easily prepared parts or portions of the flue to facilitate foolproof assembly. Another object is to carry out the just-mentioned object by means that are readily and inexpensively adaptable for coaction with other securing or anchoring means or devices. Another object is to provide, in a device of the above-mentioned character, means for facilitating precision cutting of an opening in the flue pipe and for insuring proper assembly and alinement of the device relative to both the flue and the opening cut into the flue.

Another object is to provide a device of the abovementioned character with a flue-gas-pressureu'esponsive damper and with a controllable air-admitting vent to the chimney gases constructed and arranged in a compact unit that is easily installed in an existing flue and that is adjustably associated in the unit in a manner to be readily adjusted or set to meet the widely varying conditions of combustion as well as conditions of installation met with in practice.

Other objects will be in part obvious and will be in part pointed out hereinafter.

The invention accordingly consists in the'features of construction, combinations of ,elementsgandarrangements of parts as-will be exemplifiedin-thestructure to be hereinafter described and the scope of the application vention, with a vent control part removed, showing the device in substantial readiness to' be assembled to the flue of Figure 1;

Figure 4 is an elevation as seen'from the bottom in Figure 3, showing the device, also with the vent control part removed, in relation to the flue of Figure 2 and in substantial readiness to be assembled thereto;

Figure 5 is an end elevation as seen along the line 5-5 of Figure 3, showing the device in process of assembly to the flue;

Figure 6 is a view like that of Figure 5, showing completion of the assembly of the device to the flue, with the air-vent control part omitted;

Figure 7 is a central vertical sectional view as seen along the line 7-7 of Figure 6;

Figure 8 is a side elevation as seen from the right in Figure 6, showing the completed assembly of the de vice to the flue, with the air-vent control part in position;

Figure 9 is a transverse sectionalview as seen along the line 9-9 of Figure 8;

Figure 10 is a fragmentary elevation, on a larger scale, showing a bearing assembly and shaft mounting;

Figure 11 is a side elevation like that of Figure 8, showing the complete device assembled to a flue with modified forms of locating and securing means;

Figures 12 and 13 are fragmentary vertical sectional views as seen along the lines 12 -12 and 13-13, respectively, of Figure 11, and

Figure 14 is a plan view of a template, on a much reduced scale, showing, in development, the shape and relative locations of cutouts to be made in the flue.

In the illustrative and preferred embodiment of -my invention the device, comprising a unitary assembly of a biased pressure-responsive damper and a controllably vari- .3 able air-vent for checking chimney draft, is to be installed at-aboutth'e point where the gases""of'coinbiistion lave the boiler or furnace, whence they are conducted by a flue to the. chimney;.a convenient and. preferred assemhlageof 'my device at that location comprises interrelatingriiydevice directly to the flue, preferably in close proximity, tothe furnace end of the flue, and in .Figures 1'and.2 there is 'shown1at'20' a section of such' a flue which, .for. convenience of description, has its axis horizontal; though as is later pointed outt he device maybejassembled to, and set for functioning with, a flue whose axis is vertical or at any angle between thehon'zbntal and the vertical. The arrows 'in thedrawings indicate the direc: tion'of travel of the gases of combustion so that in Figures 1. and-2 theleft hand end of therflue'is the furnaceend'and the right-hand end leads-to th'e chimneyo-rstack. The biased daniper of the device "has to be gotten into the inside erase-"fleece and-, forairadmisfsion' or draft checking the fltie 2t) has to be providedwithan air-ventior open ing, 'whil',-' on the other 'hand, the "sequential relation of dam'per :and 'ajninlet *has tobe-properlyioriented with respect to the direction bf flow or 'the' 'gasesf of combustion. Moreover,- damaging or wa'kening'niutilation of ."the flue. pipe us ually'ofsheet metal; "shouldfbe ave'oidedj "One of the dominant aims of this invention is to provide 'aconstriuetioii 1 by '-which' facile =and proper installation of "the device may be dependably effected.

lntherdr'awings I have-shown the flue 2011s 'of circular crossssectio'n, thatbeing in wide and common use; and for that :shapesof rfliie t he' saddle-lilie' frame 21 Figures;- 4; 5nai1d2693is shaped concave on its underside'of thesame radius otzthe nae-1s interfitwith the latter when set trans erselyzthereom beingof an overall extent about equal rtohhalfibf 'theperiph'ery of theflue; illustratively (see :Eigure 6.) 'lbeing of about 180 in -"extent; The frame 21 is devised io'be ina form that can be easily cast, as of caisttdrongandcitzoomprisesa central or middle portion 22 that is of relativelyi'srnall:dimension lengthwise of its of cuuvatureetbeingihowever, of substantial thickness or dimension in radial direction (see Figures 5' and 6), so" that it has substantial Lstrengthi and rigidity; i-ts under-face is,-,as fibQKCflIOICd QOIlCflQQIO match the curvature of the flneflfi; and-preferably itsupper face is also a-rcuate, being} eonvex to give it the desired radial thickness-and also, whenneated against. the-flue 20 as in Figure 6; to'cause -it a a twholeito ratherzcloselyhugthe flue and to avoid ungainlygand wasteful; projecting .parts.. With such-con formationit is.'like-.a..-strong:arcnate rib external of the flue:2Q,-is -neat innappearance, and not wasteful inmaterial Irntheillustrative embodiment it subtends an angle of about 90 or so.

Atits lends andintegrally formed or cast therewith the-central frame portion .122 has :ancuate plate-like depending and offset extensions. 23, 24,:being offset 'to theleftas viewedtin. Figures 3,,and.4; theyareiinternally concave and of the same radius of curvature as the underfaceofthe central p9rtion22, and they can be thinner than the latter, as shown'in-Figure 5, their external faces beingappropriatelyconvexfor substantial uniformity "of thickness.' throughout. Asviewed'in Figures 5 and 6, the frame portions 23, 22, 24, together-subtend an angle of about. 180", thus enveloping half of the periphery -of the fliiejfwh'enseatedtransversely-thereon as .in Fig. 6." The upper endspf the plate-like extensions 23,: 24 are provided Iwith .upstanding substantially parallel. :ribs 25, 26 'respective'lyjFigures 3, 4 and 5), and their ztop edges 1 as viewed in 5 and 3 terminate in acurvedzplane whiehicoincidels with the; surf-ace ofrevolution lot :the."

upper face of the central frame-portion, andc theaex ternal sides or faces :of .the ribs .25, 261bu1ge, outwardly, as'isbetter shown inFigures 5. and 6, forming external shallow grooves or guideways whicha're parallel to each other and'parall'elto the axis of 'the flue 20 when the frame isseated'a-gainst the latter. These ribs 25, 26 serve, at: theirztop edgefacegas spaced parallel seats for .a'

. 4 cover-plate 27, shown in Figures 8 and 9, means being pier/nearer adjustably setting the cover-plate 27 for air-inlet control, as is later described. The plate 27 is arcuate, its external surface having a radius of curvature the same as that of the top face of the central frame portion 22 (see Figure 8), but preferably the plate 27 is thinner than the frame portion 22, having an inner face of larger radius :of'curvature than the external radius of the flue 20, so that when its ends rest on the ribs 25, 26 plate 27 is held spaced from the flue 20. Externall the. plate 27 appears almost like a frame part 'o'ornpa ,to the central frame'portion 22 even thoughLLbrOader-than the latter (see Figure 8), and" at its arcuatend remote from the 'central frameportion ZZ plate '27lrasfian inwardly extending flange 28 which seats against the fiue 20, having a similar radius of curvature, and it can coast in the mounting of frame 21 onto the flue.

At its respective side end-s, as seen in Figure 9,..the cover-plate-27 terminates in parallel flanges 30', 3 1,

w h overlie the external side faces of the parallel flangi jzs: respectively, coact with the latter in slidably guiding cover-plate lengthwise of the flanges 25, 26, and 'n direcf' tions toward or away from the central 'frameportioniz; as seen in Figure 8, so as to vary at will the sizefoffthej gap, indicated at 32, therebetween, for purposes" later described; Means are provided for fixing the cover; plate 'in' its -selected position, and such means may *corn prise screws 33' (Figures 8 and 9) threaded into the flanges'30, 31 so that their free ends can engage-against" the -flanges 25, 26, preferably in the longitudinal "external" grooves in the flanges 25, 26, and in this manner the cover plate 27 may be clamped and held-in its :se'lected position." lll'i'ihe :illustrative embodiment two such "screws 33 Rare shown; one at each side flange of'the closure plate27f' being.=preferablyloc-ated, as is better-shown in 'Figure'fS} at .thelefthand ends of the flanges 30-, 31, both ofwhich" may be extendedtoward -the-left for that purpose, as? shown; Preferably, the screw end-s abut-against the down wardly, and inwardly inclined side faces of flanges 25, 26 sor=that the:clamping pressures exerted by thesc'rews'are resolved alsointo downward component-s; thus also draw-" ing-qtheplate-27 downwardly, as viewed in Figures 83am! 9, to seat it well against the tops of the fianges25, 26-and i alsoto seat the cover-plateflange 28 against-the flue'zili" The offset depending side portions 23, 24 of the frame, as :viewed in Figures 7 and 8, are provided'with bearing means vfor pivotally supporting a.damper'35=which, where' the flue is of circular cross'section, is a1so,-and--prefer-'- ably, circular. or. disk-like, but of diameter 1 materially less'than the inside diameter of the flue; somewhat as indicated iintFigures 6 and 9, in order to leavesubstan tialpassageway for gases of combustion-even whendhe damper stands at right angles to the axis -of the-flue Thedarnper 354s provided with-shaft means -for-coaction with. the bearings in the frame 21 and-conveniently,"the damper 35 and its shaft means may be cast integrally or in one piece with the axially alined pivoting shafts 36,- 37 projecting from opposite sides ofthe periphery of the-damper; in the embodiment shown the pivot shafts 36,-.37 are alined on a chord parallel to and above-the horizontal diameter of the damper (Figures 6 and 9) in order that the damper be responsive to and tiltable by thepressure of :the gases of combustionemittedby the furnace. One of the pivot shafts, 37, is longer than the otherone, 36,- andthe frame portions 23, 24 are pro videdywith round holes 38, 39, which are preferablyconsiderably larger than the diameter ofthe pivotshaftsof -thexlamper', and they may be formed by drilling or intthe course of casting-of the frame-21. Preferably,- each is providedwith a bearing which may ;be in the form of {a bushing, conveniently .in the form:of an eyelet of relatively large-diameter, which issimply set into the frame hole and its unflanged end thereupon expanded gorspun-over to holdit in places ,InFigure 9 thesemyelet them, namely, eyelet bearing, is shown on a larger scale to better indicate the coacting relationships. Preferably and conveniently, each eyelet bushing is relatively loosely mounted in its frame-hole, and it can be free to partake, of rotary-movement relative to its supporting frame part. Though the two depending frame parts 23, 24 (Figure 9) need not be geometrically parallel nor need the bearing holes 38, 39,-"therein be axially alined, the relative looseness of fit of the eyelet bearings gives the latter some leeway to more closely approximate coaxiality, and the loose fit'of the pivot shafts 36, 37 in the eyelet hearings in turn makes it unnecessary for high precision of bearing alinement.

Moreover, as the damper 35 and its pivot shafts oscillate,.i n use, relative rotary movement can take place betyleen'each pivot shaft and its eyelet bearing and also between the eyelet bearing and the frame hole in which if is loosely mounted. These coactions make for greater easefofpivoting movement or oscillation of the damper coact to prevent sticking or freezing by foreign material; For example, such relative rotary'movements tend always to shift, relatively, engaging hearing or contact surfaces, having, in efiect, a self-cleaning action, while the" axial tilt of the surface of the frame hole and of the surfaces of the loosely mounted eyelet bearing, in relation to the axis of the pivot shaft, tends to effect dis charge from these surfaces of such foreign matters as might tend to accumulate on them but are continuously loosened and shifted by the relative rotary movements ofthese parts.

The damper 35 is assembled to the frame 21 by first inserting the long pivot shaft 37 through frame'hole 39 from the inside of the frame, whence the short pivot shaft 36, by appropriate tilting of the damper unit, an action aided by the above described looseness of'the bearing mounting, is brought to the inside end of the eyelet bearing 40 and entered in to the latter to the extent permitted by stop flanges 42 (Figure 9) formed integrally with and in the plane of the damper 35 itself. The other pivot shaft 37 is provided with a hole 43 (Figure through which is then passed a cotter pin 44 (see also Figure 7) with the plane of its eye transverse of the shaft axis and with its ends wrapped in opposite directions about the shaft, as shown in Figure 7, so that it serves in effect like a peripheral shoulder or ring to coact with the inner flange of the eyelet bearing 41 to hold the damper unit 35 against shift to the right as viewed in Figure 9. The cotter pin 44 at one end and the stop flanges 42, 42 at the other end thus, in eifectthough somewhat loosely-hold the center of the damper in coincidence with the vertical center line of the frame and of the flue, holding the damper against material shift in the direction of its axis.

As viewed in Figures 9 and 6, the area of the damper below the pivoting axis is greater than the area above the axis, that being achieved, in the illustrated embodiment, by having the pivoting axis displaced from and parallel to a diameter of the damper; the damper accordingly is shiftable about its axis in response to the pressure of the moving gases of combustion when the unit is related, as later described, to a furnace or its flue, and though a substantial flow passage, annular in shape, exists between the damper periphery and the flue when the damper stands transversely of the flue, it is desirable to make provision for increasing the area of that flow passage by causing the damper to tend to assume a position that is at an angle to a plane transverse of the flue,

thus decreasing the effective size of the flow passage between the damper and the flue; I make such provision by adjustably biasing the damper 35 out of its tendency to assume a true vertical position, preferably by means of a weighted lever 46 adjustably attached to the outer projecting portion of the pivot shaft 37 (Figures 9, 6 and 4).

Weighted lever 46 is conveniently in the form of a casting, provided with a hub 47 that has a round hole therein so that it can be easily slid onto the round shaft 37, and spaced from the hub 47, and preferably outwardly offset therefrom (Figures 9 and 6), is the weighted portion 48 of the lever, conveniently cast in the form of a disk of appropriate diameter and thickness, joined to the hub by a thinner web-like portion 50. Suitable means are provided to lock the hub 47 to the shaft 37 in the desired relation of angularity of the weighted lever 46 to the damper 35, and such means conveniently comprises a setscrew 51 (Figures 9, 4 and 3).

The shaft 37 projects beyond the hub 47, and that projecting portion is shaped as indicated at 52, as by flattening two opposed sides thereof to form an acute angle (Figure 4) that simulates an arrowhead pointing in the line or plane of the damper 35 and pointing toward that side of the pivoting axis on which extends the smaller area of the damper. The indicator part 52 of shaft 37 thus always gives a visual indication of the rotary position of the damper even though the damper becomes fully enclosed within the flue, as is later described. As is better-shown in Figure 4, suitable indicia, such as the therein-indicated numbers 1, 2" and 3 may be provided on the outer end faces of the hub 47 to aid in setting the weighed lever 46 in relation to the arrowhead indicator part 52 and, hence, in relation to the plane of the damper 35 itself. Moreover, as better appears from Figures 6 and 9, the offset shaping of the weighted lever 46 insures that it is always assembled to the shaft 37 vwith the numbered hub face at the outside of the assembly; as is later explained, the lever 46 is given its desired setting after the device is installed and related to the flue 20, and even if the lever 46 were to be removed from, shaft 37 during such adjustment it cannot be reassembled thereto in reversed relation, for the offset weighted portion 48 would collide with the flue or other parts and the hub is thus prevented from' being slid onto the round portion of shaft 37.

The resultant unit, including securing and alining means later described, is compact, easily fabricated and assembled, with a minimum of machine tool operations, and its parts are so devised and so capable of assembly that very substantial dimensional tolerances are permissible, even such as include normal tolerances that accompany quantity production of parts, as by molding and casting. As above indicated, the frame 21, the closure plate 27, the damper 35 with its pivoting shafts 36, 37, and the weighted lever arm 46, can be individual castings of cast iron; the arrowhead indicator 52 on shaft 37 and the indicia on the lever hub 47 can all be cast. The eyelet bearings 40, 41 can be of relatively light sheet brass, and as above described, they fit loosely in their respective frame holes and, in turn, the pivoting shafts 36, 37 fit loosely into them, not only speeding and facilitating assembly but also achieving great ease and sensitiveness of pivoting movements of the damper 35 accompanied by self-cleaning relative rotational movements,

' movements which also coact, in effecting bit by bit turning of the loose eyelet bearings themselves, to repeatedly change or shift points or surfaces of bearing contacts. Moreover, these features of the multiple bearing structures are of long-lasting action and are well adapted to meet the widely changing temperature conditions ,of operation of the device.

In Figures 1 and 2 are shown how I prepare the flue 20 for the reception of my device. At the selected point, preferably closely adjacent the furnace, which is assumed to be at the left hand end of the flues shown in these two figures, I cut the sheet metal of the flue for the entry into itof the damper 35 and for quickly and dependably locating and securing my device in position. Transversely of the flue 20 I cut an opening, generally indicated by the reference character 55, the opening being relatively narrow and of a peripheral extent less than the peripheral extent of frame 21 but somewhat greater than the peripheral extent imposed by the above de eme 7 serih'ed multiple bearings in th'e-frame -for-the damper shafts; and geometrically positioned in relation to the cutout opening-55 Iprovide an additional cutout, preferablyin'the form oftwo round holes 56, 57, which can convenientlyjbe-made by drilling. The cutout'opening 55*has a central or middle portion 58, which is bounded by two parallel arcs 61,62, which are'of an extent at least equahto the arcuate' spacing of the upstanding flanges-25, 26 of'th'e saddle-like frame 21 of the device,

and at the side ends of this middle opening portion 58 the-cutout is extended into"sym'metricalnarrower portions63; 64, which'are otfset and inclined'toward the furnace end of the flue'20, as is clearlyv shown in Figures1 'and2." Each of these extensions or end portions 63,564, also are preferably'tapered as shown, terminating in" rounded ends of 'a'radius' materially greater than the radius of the bearingmountings for the'damper shafts, and'the 'drill holes 56; 57 "are located'in alinement on a chord of the flue"20 'and'just' below and toward the chimney sides of the offset end portion '63, 64 of the cutouts, being'accurately'located'in relation to the centers of the radii .of' the rounded ends of these cutout end portions of the opening.

Tofacilitate so preparing the flue 20, I provide a template"'6 6 shown on a smaller scalein Figure 14; it can befmade of paper and has'printed "on it, as at -67, a development'of the' above'described cutout 55, and also thecenter locations, as by the'cross marks 68, 69, of the holes 56, 57 to'be drilled'in the flue 20. Printed on it canf'al'so be suitablelegends' of instructions as suggested infl igure 14,

' Siicha template 66; after cutting out'the area within the 'line of development 67, is then fastened, as by'adlr'esive tape, transversely 'of'the selected portion of the smoke pipe orflue 20, with the linealong which the arc 61"(Figures land 2) is 'tobe cut positioned on the furnace ,side of the .flue location, according tothe printed legends of-instruction. With the template so secured theoutline 'of the development 67 'on'the template is easily markedor scored on the sheet metal, and the two holes'56;" 57 easily drilled and accurately located relative to'eachother and to the scored outline for the opening 55, whereupon the sheet metal is cut along those scorelines and the cutout 55, as described above, formed.

The'unit device, for purposes of assembly to the flue 20, mayor may not have the closure element or plate 27 "removed therefrom, but for purposes of better illustration'of the manner of assembly the closure element 27 is omittedin the views of the device as shown in Figures 3, 4, Sand 6; it has, moreover, suitable elements for coaction with the drilled holes 56, 57 of the fine, and in one form of construction these elements comprise the heads 72, 73 of bolts 74, 75 respectively, which pass through suitable holes respectively provided in the depending ofiset side portions 23, 24 of the saddle-like frame "21 and fixed in position by their respective clamping'nuts as shown, with the heads 72, 73 projecting from the inside concave face of the frame which is to interfit with the convexity of the flue 20; these holes locate the boltheads 72, 73 in the same geometrical relation to the pivoting axis of the damper 35 as the template 66 locates the holes 56, 57 in the flue in relation to the centers of the radii of curvature of the offset end portions 63, 64-of the cutout'opening in the flue; the boltheads 72, 73 are preferably of substantial size,being preferably cylindri'ca'l' in external contour and-the holes 56, 57in the flue are drilled to a size or diameter that will just neatly receive the boltheads therein.

The-bolts 74, 75-, in this embodiment, are used to clamp against the outer curved faces of the frame parts 23, 24 two-heavy sheet metal straps 77, 78 (Figures 5 and 6) which 'have their anchored ends apertured so they can b'e-slipped over the outer ends of the bolts and clamped as-afo'resaid-by the respective nuts of the latter (Figures- 3, 4 and'S) and ultimately can'extend' about the rest moved and the straps 'sp'read apart to'straddle theflil'e'f as the device, held transversely of the flue-and witli'the lower end of the damper 35 entered into the cutout open ing 55," is let down onto the "flue. As his moved downwardly in Figures 2 and 5, thelaterallyprojectingpori tions of 'the'damper '35 including'the pivotingshafts' 36,1

37 enter thecutout'extensions'63; 64 and' the 'upwardly'.* exposed downwardly inclined edges of'the latter impose" a guiding shift uponthe entire unit toward the left 'in Figures 1 and '2 as'the concave'underfa'c'e of the frame"- 21 approaches the convex surface of theflue, thereby shifting the projecting parts 72, 73 toward'holes 57, 56.. The projecting ib'olt heads 72, 73, slide along-the exterior of'the'flue, which is now purposely deformed to enter into the'holes. For example, bypressingdownwa'rdly' on the unit,'boltheads"72, 73"press opposite sidesoffthe' flue -(seeFi gui'e 5) toward 'each'other; the circular flue cross section is" distorted into a sort of oval shape (shown 'in somewhat exaggerated form in Figure '5) 'to register head 72 with hole 57 and head 73"with hole.56." or; one head'm'ay first be entered into its flue hole and the other 'used'topress the'sheet 'metal'fliie side'inwardlyf by downward'p'ress'ure onthe frame to enter it into its hole;

By' such movements, aided'by' easily elfected' mar'iu'al.

shifting and adjusting of the'unit relative to the fine, the boltheads 72, 73 are maneuvered simultaneously'or sue cessively into'registry-with the'holes' 56, 57; in either. case, due to the resiliency or spring-back ofthe sheet metal of the flue,the'inwardly pressed'si'de or side's'of the flue inelfect snap outwardly when registr'yiis achieved and thus the boltheads are-also dependably held in their respective holes.

The resultant relationship of the parts is shown in Figure '6. Thebearing structures arecentered to the cutout extensions 63, 64 and the damper 35 becomes eoncentrically'positioi'ied within the inside periphery 'of the flue 20, insuring uniform width of the annular free p'assageway which is intended to be provided by the smaller diameter of the damper 35. Suchinter'eng'agement of these projecting parts with the holes in the flue achieve a quite dependable attachment of the unit to the flue, in-that the unit device cannot' be shifted or removed without forcibly disengaging the inwardly projecting "parts from their respecti've'holes in the fine. It is preferred, how ever,'to"provide additional security of attachment so as to guard against' the chance that the person installing the device might drill' the holes tomateria'lly greater size than is appropriate'for ease of interengagcment in the manner earlier'above described, and to that end the clamping bandlmembers 77, 78 may be employed, being extended the rest 'of the way around the peri hery of the flue and put under'tension by the bolt 80, as in Figure .6. With the anchored ends ofthe straps 77, 78 attached against the outer faces of the offset frame 'parts 23, 24 respectively, the major engagement of the clamping straps. with'the flue 20 is along a substantial peripheralportion at the bott'omyof the title, as better appears in Figure 6,' with the result that the clamping action is upwardly in the direction of -the vertical diameter of the flue and acts not only to tightly seat the upper reach-(of about 1809') of the'tiue outwardly away. from each 'other'and thus insure 'against anyre'ceding movement ofthe slr'eet 'm'etal of-the flue in directions to disengage either of the projecting boltheads ,72, 73.

Such clamping action also reinforces and strengthens the flue throughout the region where it is cut out, and in this coaction the closure part 27, as is better seen in Figure 8, can also take part in that, whatever position it is given lengthwise of the parallel frame flanges 25, 26, its clamping screws 33, 33 act to draw it and its flueengaging flange 2S downwardly; with the flange 28 thus snugly and tightly seatedagainst the flue on the furnace side of the cutout 55', and with the arcuate metal portion 22 of the frame seated on the chimney side of the cutout 55,,theabove described reinforcing action on the flue becomes well distributed about the flue relative to the cutoutarea thereof.

Qther means for supplementing the securing action of the frame-projecting parts and the holes in the flue may be provided, such as shown in Figures ll, 12 and 13, where, instead of providing the clamping straps 77, 78 as abovedescribed, I provide other means for holding the sheet metal of the flue from being pressed or disftorted in directions to effect disengagement of a'project- I in'g part ofth frame from the whole in the flue, and such meanimz'iy omprise a hole 82 in each of the dependin'g' 'oflset side portions 23, 24 of the saddle-like frame '21,lo'ca ted closely adjacent the inwardly projecting part on each of these frame portions 23, 24, conveniently at points, as is indicated in Figure 11, just about midway between/the location of the inwardly projecting frame part and the location of the bearing means'in the frame. Through such a hole, after drilling a smaller hole 83 (Figure 12) in the sheet metal of the flue 20, is then driven a screw 84 of the so-called sheet metal type adapted, as is well known, to thread itself tightly into the sheet metal, thus clamping each of the two opposite sides of the flue tightly against the inner faces of the offset frame portions 23, 24. With such a coacting anchorage of the sheet metal of the flue, the inwardly projecting parts of the frame need not take the form of boltheads like those of the bolts 74, 75 above described in connection with Figures and 6, but may take any other suitable form, such as projections as shown at 85 in Figure 13 and also indicated in Figure 11, cast integrally.

The coacting locating and securing parts, meaning the inwardly projecting parts on the frame and the holes in the flue, coact to achieve other advantages; their respective relationships to the bearings and pivoting shafts of the damper 35 and to the rounded ends of the cutout extensions 63, 64 (Figures 1 and 2) are such that it is impossible to bring about a binding action or other interference between the pivoting shafts of the damper, including the eyelet bearings, with the sheet metal of the flue, the coacting parts acting so to position these parts in relation to one another that there is always substantial and, in fact, symmetrical or balanced clearance; once these projecting parts and their flue holes are interengaged it is impossible for the workman to elfect any such shift of the unit device relative to the flue as would disturb such clearances or as would achieve any other misalinement. For example, relative rotative displacement between the unit device and the flue is also dependably prevented, and thereby the opening in the saddle-like frame part 21 that is bounded by the parallel flanges 25, 26 and the arcuate middle frame portion is properly located over the middle portion 58 (Figure 1) of the flue cutout 55, and the offset side portions 25, 26 of the frame are dependably located in position to cover over the offset cut out extensions 63, 64 respectively. Moreover, it is as good as impossible to assemble the unit device to the flue with the device reversed end for end in relation to the axis of. the flue; for example, suppose that the device as shown in Figure 4 were first turned through 180 and then it was sought to let it down onto the flue 20 of Figure 2, with the damper and its shafts entering the cutout. In such case the two inwardly projecting frame parts such as the boltheads 72, 73 of Figure 5, or the parts of Figures 11 and 13, would fall in a vertical plane to the left of the downward and leftward inclined cutout extensions 63, 64 and engage side portions of the flue where there are no holes or cutouts to receive them, tending to press the flue sides inwardly and to distort the flue into a curavature with which the under side of the saddle-like frame 21 could not and would not mate; accordingly, seating of the frame in position is precluded.

With installation completed, the full unobstructed area of the middle portion 58 of the cutout, bounded by the parallel transverse arcs 61, 62 in Figures 1 and 2, and bounded at its ends by the parallel frame flanges 25, 26, is available for dependable control of entry of air from the atmosphere into the flue, by properly setting closure plate 27 lengthwise of the frame flanges 25, 26 and, as is better shown in Figure 8, toward or away from the arcuate middle frame portion 22. All that need be done is to loosen up the screws 33, 33, set the plate 27 in the desired position to give the desired vent opening at 32 in Figure 8, and tighten up the screws. The setting of the slide plate 27 may vary from a position of maximum opening for maximum inflow, of air to substantally zero opening, depending upon the charactertistics of the furnace or boiler and chimney installation. This setting is made after first setting and locking the weighted lever 46 in relation to the pressure-responsive damper 35. Here it is sought and desirable to set the weighted lever at such an angle to the arrowhead indicator 52 (Figure 4) on the damper shaft that the damper 35 is in closed position, meaning a position of minimum opening for normal furnace operation. This damper 35 may be in a plane about transverse to the axis of the flue, but usually at a small angle of tilt in opening direction as indicated in Figure 8, taking into consideration the normal pressure of the flowing gases of combustion tending to swing it in opening direction against the action of the weighted lever arm 46. The continued flow of gases of combustion to the chimney proceeds by way of the annular flow passage between the periphery of the damper and the inside periphery of the flue (see Figure 9). The resultant opposition to high velocity escape from the furnace of the hot gases of combustion in elfect backs them up somewhat within the furnace or boiler, causing them to churn more rapidly and hold and bring them into contact with heat transfer surfaces for longer time intervals and for elficient loss of heat therefrom to the medium which is to be heated by the furnace, accompanied by a more thorough scrubbing action on the furnace or boiler heat transfer areas. The device is particularly elfective with furnaces or boilers equipped with oil burners. Gases of combustion can escape to the chimney through the above-mentioned annular flow passage about the pe riphery of the damper 35; they can pass through that passage at high velocity, but their movement within the boiler or furnace and up to the damper is slowed up to give better heat transfer as above mentioned but also more thorough combustion, causing also substantial increase in the temperature within the combustion area. As a result, heat absorption or transfer to the medium to be heated within the boiler or furnace is of materially greater eflieiency, and loss of heat to the stack or chimney can be very substantially reduced.

Furthermore, the mechanism is sensitively responsive to changes in the pressure of the gases of combustion leaving the boiler or furnace; sudden increases in the pressure immediately act upon the damper 35 to tilt it further in opening direction against the action of the weighted lever arm 46, and thus such pressures are quickly relieved. The sensitiveness of pivoted mounting of the damper 35 and the above described coactions of the bearing constructions can coact toward long-lasting pressureresponsive sensitivity.

In the drawings, the device is shown, for purposes of greater ease of understanding, as applied to a horizontal,

flue or smokepipe, but as above 'notedthe device' is attachable to and adjustable to enact with a flue of any angularity including a vertical flue, so long as the axis of the damper is horizontal. All that need be done for any angle of the axis of the flue is simply to loosen up the setscrew 51 on the hub of the weighted lever 46 and, for any given or normal operating pressure of escaping gases of combustion, shift the weighted lever about the axis'of its supporting shaft 37 to, and secure it in, that position in which the torque it exerts-in closing direction on the damper 35 opposes the torque exerted in opening direction on the damper by the'pressure of the gases of combustion with the damper in as near to transverse or closed position as possible or as operating conditions dictate. The arrowhead 52 on damper shaft 37 always gives an external visual indication of the plane of the damper relative to the longitudinal axis of the flue, whatever the angularity of the flue itself.

And for any such setting of the damper and weighted lever, the closure plate 27 is set for appropriate ingress of air to the flue n the chimney side of the damper for checking draft according to whatever are the characteristics (furnace, flue, chimney, etc.) of any particular installation;-such setting of the closure plate 27 may be, as above noted, from a maximum air-inlet opening to zero and in the latter case the cutout opening in the flue is completely covered over and substantially closed 01f.

It will thus be seen that there has been provided in this invention a device in which the various objects above set forth, together with thoroughly practical advantages, are successfully achieved.

I claim:

1. A regulator installation comprising a regulator and I a sheet metal flue for conducting gases of combustion from a furnace or the like to a chimney, said flue having a cut-out opening of an overall extent about half way about the periphery of the flue and being of relatively small dimension lengthwise of the flue, said opening having a middle portion that is substantially parallelsided with narrower end portions that are offset toward the flue-gas entry end of the flue, said end being adapted to be connected to the furnace, the sheet metal of the flue having two small apertures on opposite sides thereof respectively adjacent said end portions of said cut-out opening and substantially alined on an axis that passes transversely through the flue, said regulator comprising a saddle-like frame whose under side substantially mates with the transverse contour of the flue substantially throughout the peripheral extent of said cut-out opening, said frame having a middle portion provided with an opening to overlie said middle portion of said flue opening-and depending side portions to cover over the respective narrower oii'set end portions of said flue opening, saidframe side portions being provided with alined hearing means, a damper having shaft means pivotally supported in said alined bearing means whereby, as said frame is set transversely onto said flue, said damper enters through the cut-out opening in the flue and the damper shaft means are guided by the respective oflset end portions of said flue opening to occupy positions respectively adjacent the extreme ends thereof, thereby positioning the damper axis on the side ofsaid opening that is toward said flue-gas entry end of the flue, said depending side portions having inwardly projecting juxtaposed alined projections which press opposed sides of the sheet metal flue toward one another as said'frame is set onto the flue to respectively enter said opposed apertures upon spring-back of said flue sides when respectively alined therewith and thereby locate and hold said frame and damper against shift relative to the flue and it cut-out opening and to position the frame 'soithat said opposed shaft means of the damper are out of contact with the sheet metal at said offset ends'of said' cut-out 'opening, said damper having a greater area on that side "of-its axis-of pivoting that is remotefrom" said 12 cut-out' opening whereby increase in pressure of the gases of combustion is effective'to tilt the' damper in a direction to move the damper-portion on the other side of said axis in a direction toward said flue-gas entry 4 end and awayfrom-said cut-out opening, and cover means movably associated with said frame and the opening therein for determining at will the eflective area of the opening for ingress of air into' the flue on the flue gasexit side of said damper.

2. A regulator installation comprising a sheet metal flue of circular cross section for conducting gases of combustion from a furnace or the like to a chimney, said flue having a transverse cut-out opening of an arcuate extent on the order of and of relatively small dimension lengthwise of the flue, said opening having a" middle air-entry portion that is bounded by two arcs spaced lengthwise of the flue and narrower end portions thatare inclined and offset beyond that arc that' is nearer the flue-gas entry end of the flue', said end being adapted to be connected to the furnace, said regulator comprising a rigid saddle-like frame which'on its under side has a radius of curvature equalto that of said' flue for external seating engagement with the flue, said frame comprising a middle arcuate narrow portion adapt ed to seat against the flue adjacent that boundary are that is nearer the flue-gas exit end of the flue that is adapted to be connected to the chimney and terminating in depending ofiset side portions to cover over the respective" oflset end portions of said cut-out opening in the flue; said side portions being provided with alined bearing: means carrying a damper of lesser diameter than the inside diameter of the flue, said damper having shaft means pivotally supported in said alined bearing and extending along a chord above the diameter of the damper whereby, as said frame is set transversely onto said flue, the damper enters through the cut-out opening in the flue and the damper shaft means are'guided respectively by said inclined offset end portions of said opening-to shift the frame toward said flue-gas entry end andposition the damper axis on that side of the air-entry portion of said flue opening that is toward said flue-gas entry end and'position said arcuate middle portion of the frame against the flue on the side of said flue opening that is toward said flue-gas exit end, one of said shaft means projecting beyond its associated depending side portion of the frame and having secured thereat a weighted lever arm that biases the damper to swing its lower part in the direction of flow from said flue-gas entry end to said exit end, an arcuate cover-plate overlying said air-entry portion of the cut-out flue opening and having an arcuate portion seating against the flue on the side of said cut-out opening that is toward said flue-gas entry end, and means securing said arcuate' cover-plate for adjustable movement in directions toward or away form said narrow middle portion of the frame to vary the size of the effective aperture therebetween for ingress of air.

3. A regulator installation as claimed in claim 2, in which the last-mentioned means comprise guideways on said depending side portions of the frame for coaction with the respective terminal ends of said arcuate cover plate'whereby said cover-plate may be shifted relative -to-the frame'in a'direction lengthwise of the flue, with means for holding the cover-plate in selected position relative to the frame.

4'. A- regulator installation comprising a sheet metal flue of circular cross section for conducting gases of'com-' bustionfrom a furnace or the like to 'a'chimn'ey; said flue having a transverse cutout opening'of'an' arcuateex tent on theorder of 180, said opening havingiamiddl' air-entry portion that is bounded by two arcs spaced lengthwise of the flue and end portions that are inclined and offset beyond the plane of that arcthat'isnearer'the flue-gas'entry end of the flue, said"endbein'g'adapt'ed 'to be "connected' to the furnace, said regulator comprising a 13 saddle-like frame which on its under side has a radius of curvature equal-tothat of-said flue for external seating engagement with the flue, 'said frame comprising a middle portion that is arcuateand relatively narrow adapted to seat against theflue adjacent that boundary are that is nearer theflue-gas exitnd; of the flue that is adapted to be connected to the chimney and terminating in depending offset side/portions tocover over the respective offset end portions 'of the cutout opening in the flue, said side portions having bearing means, a damper of lesser diameter than the-inside diameter of the flue and provided with shaft means whose axis extends along a chord above the diameter o f;the damper and whose ends are supported in said bearinggneafns whereby, as said frame is set transversaly' onto said :flue, the damper enters through the cutout opening-,inthe flue and the damper shaft means ente'rthe respective inclined offset end portions of said opening accompanied by shift of the frame toward said flue-gas entry end to position the damper axis on that sideof the air-entry portion of said flue opening that is toward said flue-gas entry end and position said arcuate .middle portion of the frame against the flue on that side "ufilsaid flue-opening that is toward said flue-gas exit F end; said-frame and said flue having coacting locating ineans that are interengagedtupon completion of setting lithe-frame onto the flue as aforesaid for fixing the position ofthe frame against shift about the axis of the flue and lengthwise of the flue and against movement in a direction to unseat it from the flue, and a cover-plate overlying said air-entry portion of the cutout flue opening and having means mounting it in adjustable position relative thereto to vary the size of the effective aperture for ingress of air into the flue.

5. A regulator installation as claimed in claim 4, in which said coacting locating means comprise two holes in the flue respectively underlying said depending side portions of the frame and the heads of two bolts that extendthrough said depending side portions with the heads projecting inwardly therefrom and respectively received in said holes, the outer ends of said bolts securing the respective ends of strap means that extend about the rest of the periphery of the flue and with said frame, complete the encirclement of said flue.

6. A regulator installation as claimed in claim 4, in which said coacting locating means comprise two holes in theflue respectively underlying said depending side portions of the frame and two inward projections respectively carried by said depending side frame portions and respec tively entered into said flue holes.

7. A regulator installation as claimed in claim 6, in which said depending side frame portions and portions of the flue respectively underlying said side frame portions are provided with screw means respectively threaded into said underlying flue portions for holding the latter against inward distortion to thereby prevent disengagement between a flue hole and the projecting part entered into it.

8. A regulator installation as claimed in claim 4, in which said coacting locating means comprises means projecting inwardly from said under side of said saddle-likeframe and cutout means in the sheet metal of the flue into which the projecting means is engaged by springback of the sheet metal of the flue following inward distortion thereof as said saddle-like frame is set onto the flue.

9. A regulator for assembly to a sheet metal flue that is of round cross-section and recoverably deformable into substantially oval shape, said flue having a transverse arcuate cutout opening therein and two spaced cutouts adjacent the respective ends of said opening whereby they subtend a substantial angle, said regulator comprising a saddle-like frame which is concave on its under side for external seating engagement with the flue, said frame comprising a middle portion and terminating in depending side portions, said side portions having bearing means, a damper of lesser diameter than the inside diameter of the flue and provided with shaft means and 14 whose ends project beyond the periphery of the damper and are supported in said bearing means wheroby'the damper enters through said cutout opening in the title and said ends of the damper shaft means enter the respective end portions of said opening, said frame having integral means, one for each of its depending side portions, projecting substantially radially inward fromthe curved plane of the under side thereof and subtending an angle substantially the same as the angle subtended by said spaced cutouts in the flue to thereby resist seating engagement of the frame with the flue except under forced seating movement to cause inward deformation at the sides of the line sheet metal and condition the latter forspringback to interengage with the projecting means upon the projecting means reaching respectively said spaced cutouts of the flue as seating movement of the frame continues, thereby fixing the position of the frame against shift about the axis of the flue and lengthwise of the flue and against movement in a direction to unseat it from the flue.

10. A regulator for assembly to a sheet metal flue having a transverse arcuate cutout opening therein and two spaced cutouts adjacent the respective ends of said opening whereby they subtend a substantial angle, said regulator comprising a saddle-like frame which is concave on its under side for external seating engagement with the flue, said frame comprising a middle portion that is cut out, for passage of air, where it overlies the middle portion of said cutout opening of the flue and having bearing means in its depending side portions, said side portions each having integral means projecting substantially radially inward from the curved plane of the underside thereof, said projecting means subtending an angle substantially the same as the angle subtended by said spaced cutouts in the flue, a damper of lesser diameter than the inside diameter of the flue. and provided with shaft means whose axis extends along a chord above the horizontal diameter of the damper and whose ends project beyond the periphery of the damper and are supported in said bearing means, whereby, as said frame is set transversely onto said flue, the damper enters through thecutout opening in the flue and said ends of the damper shaft means enter the opposed ends of said flue cutout opening, the ends of said inwardly projecting means on the frame forming obstructions to seating of the frame onto the fiue'excepting under force causing yielding inward distortion of the flue sheet metal for springback into interengagement with the projecting means upon the latter reaching respectively said spaced cutouts in the flue, and a cover-plate overlying said air-entry cutaway part of the frame and having means mounting it in adjustable position relative thereto to vary the size of the effective aperture forair passage.

ll. A regulator for assembly to a sheet metal flue having an external surface that is convex and having a transverse cutout opening therein, said regulator comprising a saddle-like frame which is concave on its under side to receive therein and seat against the convex surface of the flue, said frame having bearing means in its opposed ends, a damper having shaft means respectively supported in said bearing means and having a greater area on one side of the axis of said shaft means than on the other for pivotal movement of the damper in one direction in response to pressure of flue gases, one of said shaft means projecting beyond the bearing means in one of said frame ends, the projecting end being, round except for a relatively short terminal portion thereof that is conformed to provide two substantially flat converging side faces forming a pointing angle that is visible externally of the bearing means and whose bisector is in the plane of the damper, and a weighted lever arm having a hub that is slidable axially over said terminal portion that forms pointing angle and onto the round projecting end of said one shaft means to a position where said pointing angle terminal portion is visible at the outer end ems-sass tioned' in rotational direction as isvisibly determinable by reference to'the pointing angle of said terminal shaft portion and thereby give the said weighted lev'er arm a predeterminable angle to the plane of the damper according to the needed bias of the latter in opposition to the action of the flue gas pressure. 7

12. A regulator for assembly to a sheet metal flue having an external convex surface and having a transverse cutout opening therein, said regulator comprising a saddle-like frame which is concave on its under side to receive therein and seat against the convex surface of the flue,- s'aid frame having substantially self-cleaning bearing-means in its opposed ends; a damper having shaft means respectively supportedin said bearing'means whereby, as said frame is set transversely onto said flue, the damper enters through the cutout opening-in the flue and said shaft means-enter the opposed'ends of said cutout opening, each of said bearing means comprising a round hole in the end of the'frame'with its axis making a small angle to the axis of the damper shaft means and asheet metal'annulus of lesser outside diameter than said hole and-an inside diameter greater than that of the shaft means for receivingthe shaft means therein,

said annulus having end fiangesspacedapartby'a dis tance greater than the thicknessof theframe end, for freedomof rotary movement-and of changeof axial tilt of the annulus relative'to the frame holeand relative to the shaft means as said damper and its shaft' means oscillates and for thereby effect-shift and substat'itialexpulsion of-foreign matter'such-assoot ffomthe bearing;

frame which is concaveon' its-under side to receive there in and seat against the convexsurface ofthe'flue, a

damper on the concave side of said frame and pivotally supported in the opposed depending ends of said frame for entry through said cutout opening in the flue as the frame is set onto the latter, the depending ends of 'said frame each having a rigid extension integral therewith,

said extensions being juxtaposed to each other on a chord of the concave curvature of the frame with'the termini of said extensions spaced'apart bya distance less-th'anthe diameter of the flue and thereby requiring deformation of the flue into substantiallyov'al' cross-sec tionwith its major axis at substantially right anglesjto' said chord for continuation of movement of the' frame in seating direction onto'the flue, said fiuehavingat its opposed sides portions which are located on a chord parallel to the minor axis ofthe deformed flue'cross section for respective accommodation of said juxtaposed frame extensions in response to completion of seating movement and for thereby permitting spring-back of the flue to-circular cross-section with its convex surface 'engaged against the concave under side of'the saddle-like frame.

14.- A regulator 'as' claimed in claim 13, in which'said' rigid extensions comprise each alug formed integrally witli' a'nd outofthe metal of the frame and projecting" in substantially radial direction-inwardly from the re speetiv'e frame en'ds.

15-; Aregulator 'as' claimed in claim 13, in which said- 3 frame-is provided with'means, operable subsequent to the snapback-of the sheet metal of the flue, for securingthesheet' metal ofthe flue againsfthe under side of saidf'rameadjacent said fixed projecting means and hold it against forcible-distortion back into the aforesaid oval shape 16. A regulator for assembly to a sheet metal flue of substantially circular cross-section and having a trans verse cutout' opening therein, said regulator comprising a'saddle-like frtune which is concave on its underside to receive-therein and seat against the concex surface of the'tlue a 'damper on the concave side'of said frame and pi otally stipported in the opposed dependent ends of said-'-fr'am'e=for-entry through said cutout opening in the flue as the'frame'is set onto the latter, said frame having inwardly-projectingrigid means carried by and movable with the frame and positioned on the said concave undersideof the-frame toprovide a transverse spacing-less than that-provided by said concave underside of-the frame;-w'hereby to obstruct seating of said concave underside-'againstsaid' convex surface of the flue except upondistortion of the flue into substantially oval cross-section to lessen its trans-verse dimension for entry into said lesser transverse spacing and for subsequent snapback of the'flukr-upon registry of the projecting means'withappropriate' aperturemeans'in the sheet metal of the flue as interlockthe latter and said frame and hold-the fraine'seated against the convex surface of the flue, said inwardly projecting means having external surface con-- figuration that provides freedom of movement therealongiof the wallsof said aperture means under the afore- Said'snapbacltactim of the flue.

17. Aregulator-as' claimed in claim 13, provided withstrap.meansiextending from one end of said frame about the-rest--of the periphery of the flue to 'theother frameend for thereby confining the cross section of the flue against'deformation back into substantially the aforesaid-oval shape ofcross-section.

18. A regulator as claimed in claim 17, in which the ends of-said straprmeans are secured to the respective dependingends of the frame each by headed means with the headed ends thereof projecting radially inwardly.

from-the concave surface of the frame and respectively forming the aforesaid rigid extension integral with said frame ends.

References Cited in the file of this patent UNITED- STATES PATENTS DElia May 11, 1948 

